Variable capacity jet exhaust augmenter



Allg. 11, 1953 J, C;I LEE VARIABLE CAPACITY JET EXHAUST AUGMENTER Filed Sept. 27. 1949 2 Sheets-Sheet l \llllllll l llllll l.

INVENTOR lor-1N G. I EE Bvo/wwC- w AGENT Aug. 11, 1953 J, G, LEE

VARIABLE CAPACITY JET EXHAUST AUGMFNE'IEBK..1Y

Filed Sept. 27, 1949 2 Sheets-Sheet 2 INVENTOR, n JOHN G. LEE 'BVM @uw Patented Aug. 11, 195.3

VARIABLE CAPACITYJET EXHAUST AUGMEN'rIJit4 John G. Lee, Farmington, Conn., assignor to United Aircraft Corporation, East Hartford; Conn., a corporation of Delavvttre` Application September 27, 1949, Serial fNo. 117,958

6 Claims. l

This invention relates to jet propulsion units and more particularly to improved thrust augmentation mechanism for aircraft jet power plants.

Inasmuch as the propulsive force developed by the nozzle discharge of a jet power plant isa function of the mass ilow andthe velocity conditions of the ex-it gases, it is desirable to maintain the value of these parameters as near the maximum as possible. In an aircraft, during take-off where maximum thrust is required and the forward speed is low these parameters are apt to be below the maximum desirable.

In order to provide adequate take-01T power,

then, it becomes necessary to augment the thrust being developed or discharged andone method entails the introduction of added mass to the jet propulsive stream issuing from the exhaust nozzle.

It is therefore an object of this-invention to whereby the capacity of the augmenter may be varied to maintain maximum thrust until suflicient speed is obtained at the air entrance to the jet power plant.

Another object of this invention is to provide a thrust augmenting mechanism for a jet propulsion power plant which is controllable between an inoperative and a maximum augmenting position.

An object of this invention is to provide thrust augmentation in a multi-jet power plant unit to reduce thrust losses when one or more of the jet units is inoperative.

Another object of this invention is to provide a variable capacity thrust augmenter for a jet propulsion unit whereby added air is induced from the airstream passing over the power plant into the propulsive jet discharge.

A still further object of this invention is to provide a controllable augmenter which is automatically operative in response toa predetermined pressure differential.

Another object of this invention-is toprovide planned mixing of the jet exhaust of a jet power plant and the augmenting airstream to reduce the axial length of the secondary thrust nozzle which discharges the augmented ow.

A still further object of this invention is to provide a controllable thrust agumenting mechanism of the type mentioned above which includes means for planned mixing of the main jet flow and the secondary laugmenting airow;

2 the mixing being accomplished by properiypositioned vortex producingfmecha'nism.

These and-other-objects of this invention will become ymore readily .apparent from the following detailed description or the accompanying drawings in which, o

Fig.- 1 is-a cross *sectional viewof a jet propulsion unit or nacelle-whichincludesthe thrust augmentation mechanism. ofvthis invention;

Fig. `2 isa cross sectional lviewtalren along the line 2-2foffEig. l;

Fig. 3`is la .schematicdiagram of the pressure responsive electricxcontrol elementsy for-the augmentation mechanism;

Fig. 4- is across sectionrtakenkv through the line 4 4 oi-Fig. l;

Fig. A5 is af crosssectional view indicating a modified form of-vortex producing'mixing mechanism for thethrust augmenter;

Fig. Gisacross sectional view indicating a stillfurther modification of the augmenter mixing mechanism; t

Fig. 7 isfa detaiiperspective view ofthe fluid mixing rmechanism .shown in Fig. 5; and

Figs. 8 and 9 are partial cross sectional views illustrating agmcdiedadaptation;v of this invention for multi-jet units.

Referring-to; Fig. l a. jetspropulsion unit is .shownfhavingfan enclosure orcowling l0 which deiines an air intake l2' and houses a jet power plant.V i4 comprising-.a compressor |61, a burner chamber l 8,-.r aV turbine-20 and an exhaust nozzle 22. The intake I2 may contain a plurality of wallsi 23 (Figs-t 8 ^and-'9.) which divide theintake ainfor eachof the engines.

`A streamline trailingv portion 31.1y forms a continuation ofthe nacelle I0 anddenesa secondaryL exhaust nozzle 32.- The trailing portion- 30 is; axially movableffrom a position wherein the surfaces 36 and 38 are-substantially in juxtaposition to anaftextended position, as shown, thereby'y forming an annular passage, 40 which permits/.airv to be-inducted;from the airstream passingfover.theifgcowling Ill-.tobe inducted into the jet streamissuing, fromy the exhaust nozzle 22.- The kjetexhaust flowing from the nozzle 22 actsfas :an: *ejector` in' combination with the annular/passage 40 ythereby. causing an augmented mixtureof` exhaust` gases-and airto be emitted via". the secondary nozzle-32.

n In orderto axially move the trailing section 3l a plurality of jackscrews 50 arev provided including cooperating actuating sprocket type nuts 52 whichv arerota'tably fixed to adjacent nacelle structure. Thenuts 52 are rotatably driven by a chain 54 which is driven in turn by a spur gear 60 (see also Fig. 2).

A reversible electric motor 64 rotates the spur gear 60 in either direction so that by means of the jackscrew mechanism described above the aft cowling section may be extended or retracted.

A pressure responsive unit 10 may be used to control the reversible motor 64 so as to obtain the proper amount of thrust augmentation in accordance with predetermined operating requirements. To this end (Fig. 3) the unit 10 includes a flexible diaphragm 14 which separates pressure chambers 16 and 18. The chamber 16 communicates with the impact tube 11 by means of a conduit 80 and the chamber 18 communicates with the static air pressure outside the nacelle by means of a conduit 82 so that a difference in pressure in the chambers will be reiiected by a deflection of the flexible diaphragm 14. The diaphragm 14 carries an electrical contact 84 centrally thereof so that upward or downward defiection of the diaphragm will cause current to flow from the battery 86 through the contact point 88 or 90 to rotate the motor 64 in the desired direction. Thus when Contact 84 touches contact 90 the nozzle will be actuated toward a. retracted or closed position while the reverse action will ensue upon the contact 84 touching contact 88. In order to have the diaphragm 14 respond to a predetermined pressure differential a spring 14a or other biasing means may be provided for the diaphragm'14. Actually, then, the automatic operation of the control mechanism will respond to air speed.

To obtain proper thrust under the varied conditions of augmentation the secondary nozzle 32 is slightly larger in cross section than the nozzle 22. During high speed flight, then, it is preferred that a slight gap remains between the trailing surface 36 of the forward cowling portion and the surface 38 (Fig. 1) of the aft cowling section so that boundary layer air may be inducted from the outer surface of the cowl into the secondary nozzle 32 and thus maintain efficient'fiow volume there- In order to provide thorough and eflicient mixing of the primary jet exhaust and the augmenting airstreams, a plurality of fins |00 of airfoil shape may be peripherally spaced within the nozzle 32 so that they terminate in vortex-producing tips adjacent the line of convergence of the jet exhaust stream and the augmenting airstream flowing into the annular chamber 40. The fins |00 may have their chordWise dimension alternately inclined relative to the axes of now so that adjacent counterrotating tip vortices (Fig. 4) are produced which will trail downstream and provide a systemmatic planned mixing of the jet exhaust and the augmenting airstreams. In order to maintain mixing farther downstream within the nozzle 32, additional sets of fins, such as |04, may be provided. It is to be understood that the mixing described herein comprises a systemxnatic displacement type of transfer of fluid particles between the converging streams of different velocities and differs from previously well-known turbulence inducing ,mechanisms The vortex generating fins shown herein have been more fully described and claimed in copending patent application Serial No. 769,042, filed August 16, 1947, by Hendrik Bruynes which matured into Patent No. 2,558,816. As described in this patent vortex generators produce a planned mixing of fluids as distinguished from turbulence.

As shown in Fig. 5, the planned mixing between the converging streams may be effected by a plu'- rality of fins ||2 of airfoil shape which extend radially from a mast ||4 which in turn is supported by a streamline support |6 firmly secured to the walls of the secondary nozzle 32. The vortex producing fins ||9 may also be supported, as for example at ||8, at the exit of the primary jet nozzle 22 as shown in Figs. 6 and 7 and would normally include a streamlined central body |20 at their point of convergence to reduce interference between adjacent fins. The vortex producing lift surfaces |04 shown in Fig. 1 may also be utilized to maintain downstream mixing in the Figs. 5 and 6 constructions.

Figs. 8 and 9 illustrate a modified use of the thrust augmenting mechanism of this invention. In these figures a multi-jet power plant is shown having a cluster of jet engines |60 mounted in a common nacelle. Each engine has an exhaust nozzle which terminates at |62 so that the cornbined jet exhaust from all the power plants is emitted into the secondary nozzle |66. The aft cowling section |68 which defines the nozzle |66 is axially movable so that air may be inducted from outside the unit |58 into the exhaust stream to augment the thrust as heretofore described in connection with Fig. l.

The configuration shown herein (Fig. 8) has further utility in the event that one or more of the jet engines |60 become inoperative. Normally with a common exhaust nozzle a suction would be created therein at the exhaust of the particular inoperative engine to reduce the total available thrust developed by the remaining engines. In other words, when one of the engines is noperative, the common exhaust pipe fails to flow full and the separated or irregular ow which results serves to materially reduce the thrust of the remaining engines. However, with the configuration shown in Fig. 8, if one or more of the engines becomes inoperative, a switch |10 (Fig. 3) may be provided to manually extend the aft cowling section |68 to induct added air from outside the unit to fill the nozzle, thereby eliminating the separation and also augmenting the thrust being developed by the operative engines. It should be noted that in the event one of the power plants becomes inoperative the tendency would be to decelerate the aircraft and reduce the total pressure so as to urge the contact 84 toward contact 88 rather than contact 90. Operation of switch |10 toward a nozzle extended position would hence not be hindered by the automatic control. However in order to have the switch |10 take over positive control of the reversible motor 64 under all conditions it would be an obvious expedient to provide a means for overriding the automatic control, For example, a. switch may be interconnected with the manual control to disable the automatic control when the switch |10 is moved from its mid-position. Even a relay or a mechanical disabling means would be another obvious expedient since the manual control would be intended to provide primary control of the motor upon actuation thereof. In this manner the mass discharge fiowing through the nozzle |66 will be maintained at an efficient value and the suction or drag within the nozzle resulting from the inoperative engine will be eliminated. In Figs. 8 and 9 the vortex producing fins |9a may be used to produce efllcient planned mixing of the streams to shorten the required length of the secondary nozzle.

In operation then, during take-off for example, a certain differential will exist between the im.f

pactfand static pressures of the outside airstrea'm :so lthat the diaphragm 1.4.of the .pressure responsive .unit 1u will causethe .engagement of the lcontact points. 88..with contact. 84 to rotate the motor G4 and by .meansof the jackscrew mechanism extend thetrailing portion 30. of the `cowling (to the. Fig. r1 position) to'form lan ejector which will .induct Vair via theannular chamber 40 to augment the jet .exhaust flowing from the nozzle 22. The Vaforementioned streams of exhaust gas and air will then be thoroughlyl mixed Within the secondary nozzle 32 by means of the vortex producing fins i011 and will -be-ejected therefrom as an augmented stream producing an increased zthrust dur-ing take-off. It'should be noted that ashigher speed is attained the pressure responsive unit will tend to operate in the reverse direction to retract the trailing portion 30.

In a multi-engine jet unit discharging exhaust from a common nozzle (Fig. 8) the pilot may, upon failure of one of the engines IBD, operate the switch |10 (Fig. 3) to extend the aft section |68 of the cowling to increase the augmentation as required and reduce the suction adjacent the point |62 of the engine exhaust nozzle,

It is therefore apparent that as a result of this invention an improved thrust augmenting mechanism has been provided which operates automatically at relatively low forward speeds and which in its substantially inoperative position forms a streamline continuation of the jet unit enclosure thereby producing negligible drag at high speeds.

Also as a result of this invention, a simple, rugged and eiiicient thrust augmenting mechanism has been provide which will effectively increase the thrust of jet propulsion units at low, usually ineflicient, forward speeds.

Although certain embodiments of this invention have been shown and described above, it is obvious that various changes and modications may be made in the shape and arrangement of the various parts without departing from the scope of this novel concept.

What it is desired by Letters Patent is:

1. In a jet propulsion unit for an aircraft, an exhaust nozzle for discharging a propulsive jet stream from said unit, a variable capacity ejector mechanism for withdrawing air from without said unit into said stream, and means for mixing said air and said stream including a plurality of lift producing airfoil shaped surfaces peripherally spaced around the wall of said ejector mechanism and terminating in tips adjacent the line of convergence of said air and jet stream, adjacent surfaces being oppositely inclined relative to the axis of flow whereby adjacent counterrotating trailing vortices are produced from the tips thereof.

2. In a jet propulsion unit for an aircraft, a jet engine, an air intake and an exhaust duct for said engine, a main nozzle for directing a propulsive jet stream from said engine exhaust duct, and means for augmenting the propulsive thrust of said jet comprising an extension nozzle forming a part of said main nozzle, said extension nozzle having a cross-sectional area greater than said main nozzle, means for axially separating said nozzles to induct air from the airstream into said extension nozzle, comprising, means responsive to a differential of pressures for varying the amount of separation of said nozzles including a pressure responsive element, and electrical power means controlled by said element and operatively "'c'om'iected1'y to ffsaid' vzextensi'on nozzle for :axially moving the flatter, `a ssetboffaerodynamic -vlift .surfaces peripherally :spa-ced :adjacent the; jet stream issuing from'said main nozzle and terminating in vortex producing tips adjacent the line of convergence ofsaid air-and jet streamsfor increasing the mixingl therebetween, and 4at least one additional" set0 of'aero'dynamic vlift Vsurfaces protruding.;.from the inner wall; of said extension znozzledownstream of said .fi-rst .mentioned vset .and terminating. in vvortex producing tips for maintaining said .mixing in saidaugmented jet stream each setof lift. surfaces having adjacent 'surfaces 'withtheir chordwise dimensionsv .oppos'itelyinclined relativeto theaxis of thestream.

13. Infa.jet..propulsion...unit for an aircraft, a plurality of power plants, a plurality of exhaust nozzles for said power plants terminating in adjacent relation whereby a substantially common jet stream issues therefrom, a variable capacity ejector for inducting air from outside said unit to augment the thrust of said jet stream including a secondary nozzle for receiving said jet stream, and means for reducing drag in said jet stream and causing said stream to flow full in said secondary nozzle when any of said power plants is inoperative including manually operated control mechanism for varying the capacity of said ejector.

4. In a jet propulsion unit for an aircraft, a plurality of power plants, a plurality of exhaust nozzles for said power plants terminating in adjacent relation'whereby a substantially common jet stream issues therefrom, a variable capacity ejector for inducting air from outside said unit to augment the thrust of said jet stream, means responsive to the speed of the aircraft for automatically varying the capacity of said ejector, and means for reducing drag in said jet stream when any of said power plants is inoperative including manual control mechanism for varying the capacity of said ejector.

5. In a jet propulsion unit for an aircraft, a plurality of power plants, a plurality of exhaust nozzles, one for each of said power plants, terminating in adjacent relation whereby a substantially common jet stream issues therefrom, a variable capacity ejector for inducting air from outside said unit to augment the thrust of said jet stream comprising a secondary nozzle axially movable relative to said exhaust nozzles and adapted to receive said jet stream, means for eliminating suction drag within said secondary nozzle and causing the received stream to fill said secondary nozzle when any of said power plants is inoperative comprising electrically operated control mechanism for axially moving said secondary nozzle and means providing planned intermixing in said secondary nozzle between the jet stream and the induced air.

6. In an ejector mechanism for augmenting the thrust, a jet propulsion unit, a jet exhaust nozzle for said unit, a secondary nozzle for receiving the jet from said exhaust nozzle, cooperating means carried by said nozzles forming a passage for inducting air from without said engine to augment said jet, pressure responsive means for moving said secondary nozzle along the axis of iiow for varying the size of said passage, and means for mixing the exhaust and inducted airstreams comprising vanes of airfoil shape located in one of said streams and terminating in tips adjacent the line of convergence of the streams whereby trailing tip vortices are produced having their axes substantially coincident with said line of convergence, adjacent vanes having their chordwise dimensions oppositely inclined relative to the axis of jet flow.

JOHN G. LEE.

References Cited in the file 0f this patent UNITED STATES PATENTS Number Name Date Re. 23,149 Lubbock et al Sept. 20, 1949 1,369,672 Koenig Feb. 22, 1921 1,405,482 Bostedo Feb. 7, 1922 1,493,753 Koleroff May 13, 1924 1,546,262 Stahl July 14, 1925 1,605,484 Thompson et a1 Nov. 2, 1926 1,637,347 Nelson Aug. 2, 1927 Number Number l5 587,558

Name Date Sauer Oct. 1, 1940 Sherman Sept. 24, 1946 Alexanderson Nov. 9, 1948 Whittle Dec. 7, 1948 Price Nov. 8, 1949 Hepburn Nov. 22, 1949 Martin May 30, 1950 Wallace Sept. 26, 1950 Neal Nov. 6, 1951 Whittle June 17, 1952 FOREIGN PATENTS Country Date Great Britain Apr. 29, 1947 Great Britain Dec. 17, 1948 

